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Diagnoses of peanut allergy in children under three years classic have decreased by 43 percent since 2017, according to a U.S. Study published last October. This shift in allergy rates is a significant development for families with children at risk, and researchers are exploring the reasons behind the decline.
The improvement appears linked to a change in medical recommendations. On January 5, 2017, the National Institute of Allergy and Infectious Diseases updated its guidelines, suggesting that introducing peanuts early in life—even in the first few months—could help prevent allergies in at-risk infants. This was a reversal of previous advice.
For nearly two decades prior, the American Academy of Pediatrics recommended that parents delay introducing allergenic foods to infants considered at risk. Families were advised to wait one year after birth before introducing cow’s milk, two years for eggs, and three years for peanuts and fish. The rationale was that postponing exposure would reduce the risk of an unwanted immune response.
These 2000 guidelines were a response to what was perceived as an “epidemic of allergies.” Schools began establishing “peanut-free zones,” and epinephrine auto-injectors—often called EpiPens—became commonplace in teachers’ desks and students’ backpacks to address potential allergic crises. Between 1997 and 2008, the prevalence of peanut allergy more than tripled among U.S. Children, rising from 0.4 percent to 1.4 percent. Similar trends were observed in the United Kingdom, Australia, and other Western countries.
Gideon Lack, a pediatric immunologist at King’s College London, was among the experts concerned by this increase. In 2000, while speaking at a conference in Tel Aviv, Israel, he asked the audience of allergists and pediatricians how many had seen at least one patient with a peanut allergy in the past year. In a U.S. Or London auditorium, nearly all hands would have risen. In Tel Aviv, Lack counted only two or three. Why were fewer children in Israel developing this allergy?
To investigate, his research team compared more than 10,000 children of Jewish heritage—half from the United Kingdom and half from Israel. Many British and Israeli Jewish families shared a similar ancestral background, allowing researchers to isolate the impact of genetics versus other factors. They found that the percentage of allergic children was 1.85 percent in the United Kingdom, but only 0.17 percent in Israel. Further investigation revealed that Israeli children commonly consumed Bamba, a peanut-based snack, while British children generally avoided peanuts until age three, following the prevailing recommendations.
The study, published in 2008 in the Journal of Allergy and Clinical Immunology, showed an association between early peanut consumption and lower allergy rates, but didn’t prove cause and effect. This led Lack to design the LEAP trial, or Learning Early About Peanut Allergy. 640 infants at high risk for peanut allergy—due to existing egg allergies or skin inflammation—were divided into two groups. One group regularly consumed peanuts from infancy, while the other avoided them until age five. The results demonstrated that consuming six grams of peanut protein per week reduced the risk of developing an allergy by 81 percent. Subsequent studies showed this effect persisted into adolescence, with children who had eaten peanuts in their first five years of life having a 71 percent lower likelihood of being allergic.
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The key isn’t that peanuts “cure” allergies, but rather how a baby’s immune system learns to distinguish between food and a threat. At birth, the immune system doesn’t yet know what is dangerous and what isn’t. This learning process is influenced by factors like gut bacteria and skin health. When this learning is disrupted, the immune system may misidentify a harmless protein as a threat.
According to Lack’s “dual allergen exposure hypothesis,” the way the immune system first encounters a protein can determine how it’s classified. When a food protein reaches the gut, cells recognize it as food and promote tolerance. Still, the initial encounter could occur elsewhere, leading to sensitization—a process that makes the body reactive to a specific allergen.
Sensitization can occur through inflamed skin. Intact skin acts as a barrier against foreign substances. However, when compromised—as in eczema—proteins can penetrate the skin. This triggers an immune response, potentially classifying food proteins as threats and prompting the body to create specific antibodies.
A subsequent encounter with that food protein then triggers the release of antibodies, activating mechanisms that cause swelling, inflammation, and other allergy symptoms. The child may not have even tasted the food yet, but is already immunologically primed to react. “For years we thought that food allergies caused eczema,” Lack told CNN. “Now we know that it’s the other way around,” although the relationship is still being investigated.
Following the LEAP trial results, many countries updated their allergy prevention guidelines. The long-term effects of these changes are still being studied. While trials like LEAP demonstrate effectiveness in controlled settings, real-world implementation—across diverse families and food cultures—may yield different results.
The 43 percent decrease observed in the U.S. Study should be interpreted cautiously. Some researchers point out that this number may reflect methodological factors, such as focusing only on severe allergy cases. Further skepticism is fueled by data from a large-scale survey showing that only 29 percent of U.S. Pediatricians fully implement the new guidelines. In Australia and Sweden, where recommendations changed similarly, the decline in diagnoses was more modest. One explanation may be that in Australian families who introduced peanuts in the first year of life, less than 30 percent consumed them more than once a week, as was the case in the LEAP trial.
These differences could also be due to varying allergy prevalence, dietary habits, or home environments. Guidelines are not universally applied. European guidelines specify that early peanut introduction is particularly recommended in countries where allergies are common. Italy is not among these.
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In Italy, peanuts are not a staple food, resulting in fewer opportunities for sensitization and a lower incidence of allergies. Italy hasn’t experienced the same history of avoiding early peanut exposure seen in the United States or the United Kingdom.
To understand the current situation in Italy, EPIFA—a study published in 2024 and coordinated by Roberto Berni Canani, a pediatrician and researcher at the University of Federico II of Naples—serves as a key reference. Analyzing data collected in Campania between 2009 and 2021 from over 105,000 children and adolescents, researchers documented a roughly one-third increase in the overall number of children with food allergies, while new cases more than doubled. The most common allergens are cow’s milk, eggs, and tree nuts.
The authors explain that this increase may be due to several factors, including increased awareness among parents and doctors, improved diagnoses, and changes in dietary and environmental habits. Food allergies in children are becoming more visible and likely more frequent; however, the relative contribution of each factor remains unclear.
Today, desensitization treatments are also available. Oral immunotherapy involves daily ingestion of a small dose of the allergen, gradually increased every few weeks for months. It doesn’t “cure” the allergy, but raises the threshold at which the immune system reacts. For many families, this difference is significant—it means living with less fear of accidental exposure and knowing that a trace amount in a cookie won’t cause a severe reaction.
Many uncertainties remain. However, we now know that the immune system can be modulated and that the first few months of life are a crucial period for this process. This represents a much stronger starting point than existed two decades ago.
